MySQL

取中值

这是一种思路，通过 GROUP_CONCAT 把多个数值按顺序组合成字符串，再通过 SUBSTRING_INDEX 取出中间的值。

table

CREATE TABLE `yager`.`prices` (
  `product_id` int NOT NULL,
  `price` int NOT NULL
);

query

select r.product_id, 
    SUBSTRING_INDEX(SUBSTRING_INDEX(r.prices, ',', CEIL(r.total/2)), ',', '-1') AS price_mid 
from (
    select GROUP_CONCAT(price ORDER BY price) as prices, 
        product_id,
        COUNT(*) as total 
    from `prices`
    group by `product_id`) 
as `r`;